Weathering Flashcards
Bio weathering
The action of growing/decaying plants, breaking down minerals in rocks.
Chemical weathering
Decomp of rock, the breakdown of chemical structures of the minerals of its composition
The rate of chemical weathering is
Related to the amount of biological activity
Mafic minerals / rocks weather more easily than
Felsic minerals / rocks
Physical weathering - rock shattering
Expansion and contraction of rocks heating and cooling. In dry desert climates.
Physical weathering - freeze thaw
Common on mountain tops.
Infiltration of water, which freezes and expands,by 9%, causing pressure and forcing rock apart.
Physical weathering - onion skin
Out portion of rock expands when pressure is relieved
Physical weathering is the
Mechanical process that separates rock particles.
Physical weathering - jolting
Initiates physical weathering because of pressure release from rocks at the surface. Causes expansion and results in rocks breaking and splitting, forming joints.
How water becomes acid
Rainwater dissolves carbon dioxide from the air. Result is H+ ions and hydrogen carbonate ions HCO3-. The solution is a very weak acid. Results I. The dissolution of carbonate rocks.
Re precipitated carbonate rocks form
Due to the slow evaporation of hydrogen carbonate rich waters.
Why is weathering dependent on latitude and climate? (4)
Chemical weathering is more rapid in high temps and high precipitation (tropics)
Higher rainfall = rapid leaching of ions
Warm, damp, acidic conditions = further breakdown of silicate structures.
Desert regions - lack of chemical weathering because of lack of water and vegetation. Physical weather dominates (much slower)
The formation of hydrated oxide clays
Under conditions of intense weathering (tropics)
Formed by a reaction of iron, aluminium and magnese in ionic form, with water and oxygen.
